Quality of the primate photoreceptor lattice and limits of spatial vision

Quantitative analysis of a primate photoreceptor lattice shows that the foveal lattice is a highly regular hexagonal structure with a positional correlation length of at least 130 photoreceptors. This result indicates that the photoreceptor lattice is not sufficiently disordered to prevent aliasing in the fovea. but rather could provide the metric with which the visual system determines spatial separation even for tasks involving hyperacuity.     

A new model of retinal photoreceptor cell degeneration induced by a chemical hypoxia-mimicking agent, cobalt chloride

Retinal photoreceptor cell degeneration was induced by cobalt chloride, a chemical hypoxia-mimicking agent in rodents. Time course and dose-response of photoreceptor cell degeneration in mouse retina after intravitreal injection of cobalt chloride were examined by conventional histological analysis by hematoxylin and eosin staining and in situ terminal dUTP-biotin nick end labeling of DNA fragments (TUNEL) method with the use of paraffin-embedded sections. The dose-response of photoreceptor cell degeneration in rat retina was also examined. Photoreceptor cells progressively degenerated with time and under dose-response relationship. The suitable dose of cobalt chloride for the selective photoreceptor cell degeneration in mice is 10-12 nmol intravitreal injection at the volume of 2 microl. The retinal morphology of the mice 2 weeks after the 10-12 nmol intravitreal injection was similar to that of retinal degeneration in the mutant rd mouse. Retinal damage of total retinal layers was induced by an excessive dose of cobalt chloride. The progression of retinal damage after cobalt chloride injection, measured morphologically, was completed at 1 week. However, nuclear DNA fragmentation, mainly detected at outer nuclear layer by TUNEL, peaked at 48 h after 12 nmol cobalt chloride injection. Thus, the selective photoreceptor cell degeneration induced by cobalt chloride follows DNA fragmentation at outer nuclear layer. The photoreceptor cell degeneration is established optionally by cobalt chloride without use of the retinal degeneration mutant animals. Thus, we have described the development of a new model of retinal photoreceptor cell degeneration induced by a chemical hypoxia-mimicking agent.     

Cellular strategies for retinal repair by photoreceptor replacement

Loss of photoreceptors due to retinal degeneration is a major cause of blindness in the developed world. While no effective treatment is currently available, cell replacement therapy, using pluripotent stem cell-derived photoreceptor precursor cells, may be a feasible future treatment. Recent reports have demonstrated rescue of visual function following the transplantation of immature photoreceptors and we have seen major advances in our ability to generate transplantation-competent donor cells from stem cell sources. Moreover, we are beginning to realise the possibilities of using endogenous populations of cells from within the retina itself to mediate retinal repair. Here, we present a review of our current understanding of endogenous repair mechanisms together with recent progress in the use of both ocular and pluripotent stem cells for the treatment of photoreceptor loss. We consider how our understanding of retinal development has underpinned many of the recent major advances in translation and moved us closer to the goal of restoring vision by cellular means.     

Central Photoreceptor Viability and Prediction of Visual Outcome in Patients with Idiopathic Macular Holes

Purpose

To identify the correlation between preoperative optical coherence tomography (OCT) features and postoperative visual outcomes in eyes with idiopathic macular holes (MHs).

Methods

Data from 55 eyes with idiopathic MHs which had been sealed by vitrectomy were retrospectively reviewed. Correlation analysis was conducted between postoperative visual acuity (V_postop, logarithm of the minimum angle of resolution [logMAR]) and preoperative factors, including four OCT parameters: the anticipated length (A) devoid of photoreceptors after hole closure, MH height (B), MH size (C), and the grading (D) of the viability of detached photoreceptors. Additionally, the formula for the prediction of visual outcome was deduced.

Results

V_postop was determined to be significantly correlated with the preoperative visual acuity (V_preop) and OCT parameters A, C, and D (p<0.001). Based on the correlation, the formula for the prediction of V_postop was derived from the most accurate regression analysis: V_postop=0.248×V_preop+1.1×10^-6×A²-0.121×D+0.19.

Conclusions

The length and viability of detached photoreceptors are significant preoperative OCT features for predicting visual prognosis. This suggests that, regardless of the MH size and symptom duration, active surgical intervention should be encouraged, particularly if the MH exhibits good viability in the detached photoreceptor layer.     

Reorganization of photoreceptor layer on optical coherence tomography concurrent with visual improvement after macular hole surgery

To report three cases in which reorganization of the photoreceptor layer on optical coherence tomography (OCT) was concurrent with long-term visual recovery after macular hole surgery. Serial OCT scans of three eyes in which visual acuity continued to improve for 1 or more years after successful macular hole surgery were reviewed. Case 1. At postoperative four weeks, visual acuity was 20/100 with disorganized photoreceptor layer on OCT. The photoreceptor layer had been reorganized and visual acuity had improved to 20/25 by 1 year. Case 2. Two weeks after the operation, visual acuity was 20/125 and disorganization of the photoreceptor layer was noted. Visual acuity improved to 20/50 by four months. The photoreceptor layer had been partly reorganized and had appearance of a broken line. Visual acuity had improved to 20/40 and the photoreceptor layer had been reorganized further with a residual defect on OCT by 15 months. Case 3. Visual acuity at two weeks was 20/100. OCT revealed disorganization of the photoreceptor layer. Six months after the operation, the partly reorganized photoreceptor layer appeared as a broken line and visual acuity had reached 20/80. Visual acuity had improved further to 20/40 by 1 year, concurrent with improved organization of the photoreceptor layer. The reorganization of the photoreceptor layer plays a part in long-term improvement of visual acuity after macular hole surgery.     

Identification of novel retinal target genes of thyroid hormone in the human WERI cells by expression microarray analysis

Using the human WERI-Rb1 cell line as a model system, we performed a genome-wide search for retinal target genes of thyroid hormone (TH) via expression microarray analysis followed by quantitative real-time RT-PCR verification. We identified 12 novel retinal targets of TH, including 10 up-regulated genes (OPN1MW, OPN1LW, TIMP3, RP1L1, GNGT2, CRX, ARR3, GCAP1, IMPDH1, and PDE6C) and 2 down-regulated genes (GNGT1 and GNB3). In addition, we found a number of novel TH-targets that are not currently known to be retinal genes. This is the first report of human retinal targets regulated by thyroid hormone.     

与蝇追逐行为有关的复眼性特异光感受器的研究

本工作研究野生家蝇复眼的不同区域光感受器和第一视神经节的显微及亚显微结构,以及光感受器细胞轴突向视中枢的投射。结果表明,雄性家蝇复眼的背前区和赤道区、雌性家蝇复眼的腹前区,在网膜和第一视神经节(薄板)的形态结构和网膜向薄板投射的关系上,都呈现出与蝇的追逐行为明显相关的性别特征。     

视网膜中央静脉阻塞黄斑水肿患者中心凹光感受器层状态与视力的相关性

目的:研究视网膜中央静脉阻塞(CRVO)伴黄斑水肿(ME)患者视力与中心凹部光感受器层状态间的相关性。方法:回顾性分析CRVO伴ME患者21例21眼行玻璃体腔内注射曲安奈德(IVTA)之前以及治疗后4周视力及光学相干断层扫描(OCT)影像中视网膜内外光感受器的连接部(IS/OS)的状态。结果:注射IVTA后4周,本组研究中所有患者ME均明显消退。IS/OS(+)组,11眼(52.3%)可以观察到中心凹处部分或完整的IS/OS线。IS/OS(-)组,10眼(47.62%)中心凹处IS/OS线影响缺失。治疗前后两组患者视力及中心凹厚度的改变均具有统计学意义而且治疗前患者的视力情况与IS/OS的状态存在明显的相关性。结论:对于CRVO伴ME患者的治疗,在消除黄斑水肿的同时应该注重对中心凹部光感受器细胞的保护。     

Water escape performance of adult RCS dystrophic and congenic rats: a functional and histomorphometric study

The dystrophic Royal College of Surgeons (RCS) rat undergoes photoreceptor degeneration due to a hereditary defect in the retinal pigment epithelium. The congenic rat remains unaffected. Although the retinal degeneration is well characterized, few functional studies of this strain are available. We wished to compare the visual function of congenic and dystrophic RCS rats using a water escape paradigm that tested their ability to find a submersed, randomly placed platform using a light source as a clue. Three different behavioral experiments were sequentially performed on all animals: Experiment 1—The Light and Platform test measured the time to swim from the center of the pool to a platform located under a light clue. Each animal was given 10 trials. Experiment 2—The No Light with Platform test was performed as above except no light clue was used. Experiment 3—The Light and No Platform test was performed with a light clue but without a platform. The animal was allowed to swim for 2 min. All trials were videotaped. After the final experiment, the animals were sacrificed and a histomorphometric analysis of their retinas were performed. Expt. 1—The time to find the platform using light as a clue was greater for the dystrophic than for the congenic rats. Expt. 2—In the absence of light clue, there was no significant difference in performance between the congenic and dystrophic animals. Expt. 3—In the absence of a platform, a significantly greater amount of time was spent in the area indicated by the light clue by the congenic animals as compared to the dystrophic. Morphometric analysis revealed a mean number of 133 photoreceptor nuclear profiles/90 μm of retina for congenic rats as compared to 0.14 for dystrophic rats. This simplified version of the Morris water maze permits quantitative evaluation of visually-guided behavior in an important model of retinal degeneration.